The present invention generally relates to a semiconductor device incorporating circuit elements that are formed of refractory metal-silicon-nitrogen and a method for such fabrication and more particularly, relates to a semiconductor device that incorporates circuit elements such as resistors, capacitors, fuses and diffusion barriers that are formed of metal-silicon-nitrogen and method for such fabrication.
In semiconductor devices, capacitors, fuses and diffusion barriers are frequently formed in-situ in the semiconductor structure, while resistors are typically connected to a circuit board external to the semiconductor structure to provide required electrical resistance to an electronic circuit.
It is therefore difficult to provide resistors that are built in-situ in a semiconductor structure. It is particularly difficult to form in-situ resistors in a semiconductor structure to provide high resistance, i.e. to provide resistance in the range of more than several thousand xcexa9/sq. For instance, a resistor designed for use in a semiconductor device has been a diffusion resistor that is built on the surface of a semiconductor substrate. The sheet resistance of a diffusion resistor is typically in the range between about 100 xcexa9/sq. and about 4,000 xcexa9/sq. Moreover, it has not been possible to build unit resistors inside a semiconductor structure arranged in a vertical direction due to the unavailability of a material that can be used in a semiconductor process which has sufficiently high electrical resistivity and thermal stability.
While refractory metals have been frequently used in semiconductor processes to form vias or contacts, refractory metal-nitrogen alloys have not been widely used in the processing of semiconductor devices. For instance, only recently U.S. Pat. No. 5,892,281 described the use of tantalum-aluminum-nitrogen alloys in semiconductor devices as a diffusion barrier and an adhesion promoter. The patent discloses the use of Taxe2x80x94Alxe2x80x94N in a semiconductor device to prevent inter-diffusion between surrounding layers, for instance, between two conductor layers, between a semiconductor layer and a conductor layer, between an insulator layer and a conductor layer, between an insulator layer and a semiconductor layer, or between two semiconductor layers. A second use of Taxe2x80x94Alxe2x80x94N is to promote adhesion with adjacent layers, for instance, between two conductor layers, between a conductor layer and an insulator layer, between a semiconductor layer and a conductor layer, or between two semiconductor layers. However, U.S. Pat. No. 5,892,281 does not teach any other uses for tantalum-aluminum-nitrogen alloys in semiconductor devices.
It is therefore an object of the present invention to provide a semiconductor structure that contains at least one circuit element fabricated of refractory metal-silicon-nitrogen that does not have the drawbacks or shortcomings of conventional semiconductor structures.
It is another object of the present invention to provide a semiconductor structure that contains at least one circuit element selected from the group consisting of a fuse, a resistor, a trimable resistor, a diffusion barrier and a capacitor that is fabricated of a refractory metal-silicon-nitrogen alloy.
It is a further object of the present invention to provide a semiconductor structure that contains at least one circuit element in the structure that is fabricated of tantalum-silicon-nitrogen.
It is another further object of the present invention to provide a semiconductor structure that contains at least one circuit element that is fabricated of tantalum-silicon-nitrogen which contains between about 10 at. % and about 55 at. % Ta, between about 10 at. % and about 45 at. % Si, and between about 30 at. % and about 80 at. % nitrogen.
It is still another object of the present invention to provide a semiconductor structure that contains at least one resistor, at least one trimable resistor, at least one capacitor, at least one fuse and at least one diffusion barrier which are fabricated of refractory metal-silicon-nitrogen.
It is yet another object of the present invention to provide a method for fabricating a semiconductor structure that contains a fuse element by first forming a fuse element of refractory metal-silicon-nitrogen, and then ion-implanting the element to substantially increase its resistivity.
It is still another further object of the present invention to provide a method for fabricating a semiconductor structure that contains a trimable resistor element by first forming the element in refractory metal-silicon-nitrogen, heat treating the element to induce crystallinity, and then forming the element of lower resistivity.
It is yet another further object of the present invention to provide a method for fabricating a semiconductor structure that contains a diffusion barrier layer by first forming an electrical contact on top of a semiconductor substrate, and then depositing a layer of refractory metal-silicon-nitrogen on the electrical contact to form the diffusion barrier layer.
In accordance with the present invention, a semiconductor structure that contains at least one circuit element that is fabricated of refractory metal-silicon-nitrogen and a method for fabricating the semiconductor structure are provided.
In a preferred embodiment, a semiconductor structure is provided which contains at least one circuit element selected from the group consisting of a fuse, a diffusion barrier, a resistor, a trimable resistor, and a capacitor; the at least one circuit element is formed of refractory metal-silicon-nitrogen.
The semiconductor structure of the present invention may further include a pre-processed substrate formed of a semi-conducting material or of an electrically insulating material. The refractory metal in the refractory metal-silicon-nitrogen may be selected from the group consisting of Ta, Nb, V, W and Ti. The refractory metal-silicon-nitrogen may be TaSiN which contains between about 10 at. % and about 55 at. % Ta, between about 10 at. % and about 45 at. % Si, and between about 30 at. % and about 80 at. % N. The semiconductor structure may further include at least one conductive element in electrical communication with the at least one circuit element, the at least one conductive element may be formed of a material selected from the group consisting of doped polysilicon, metal silicide, polycide, refractory metal, aluminum, copper and alloys thereof.
The present invention is further directed to a semiconductor structure that contains at least one resistor, at least one trimable resistor, at least one capacitor, at least one fuse and at least one diffusion barrier; the at least one resistor, the at least one trimable resistor, the at least one capacitor, the at least one fuse and the at least one diffusion barrier may be formed of refractory metal-silicon-nitrogen. By trimable resistor, it is meant a resistor which has a resistance value that is tunable by heat treatment.
The semiconductor structure may further include a pre-processed substrate onto which the at least one resistor, the at least one trimable resistor, the at least one capacitor, the at least one fuse and the at least one diffusion barrier are formed. The pre-processed substrate may be a silicon wafer. The refractory metal in the refractory metal-silicon-nitrogen may be selected from the group consisting of Ta, Nb, V, W and Ti. The refractory metal-silicon-nitrogen may be TaSiN which contains between about 10 at. % and about 55 at. % Ta, between about 10 at. % and about 45 at. % Si, and between about 30 at. % and about 80 at. % N.
The present invention is further directed to a method for fabricating a semiconductor structure that contains a fuse element which may be carried out by the operating steps of first providing a pre-processed substrate, forming a fuse element of refractory metal-silicon-nitrogen on the substrate; and ion-implanting the fuse element and increasing the sheet resistance of the fuse element to at least 3000 xcexa9/xe2x96xa1.
The method for fabricating a semiconductor structure that contains a fuse element may further include the step of selecting a refractory metal for the refractory metal-silicon-nitrogen from the group consisting of Ta, Nb, V, W and Ti. The method for fabricating a semiconductor structure that contains a fuse element may further include the step of forming the fuse element with TaSiN. The composition of TaSiN may contain between about 10 at. % and about 55 at. % Ta, between about 10 at. % and about 45 at. % Si, and between about 30 at. % and about 80 at. % N. The method may further include the step of ion-implanting the fuse element with N/Si and/or O. The method may further include the step of implanting the fuse element with N/Si and/or 1 at an implantation dose between about 1xc3x971014 atm/cm2 and about 1xc3x971016 atm/cm2.
The present invention is still further directed to a method for fabricating a semiconductor structure that contains a trimable resistor element which includes the steps of first providing a pre-processed substrate; forming a trimable resistor element of a refractory metal-silicon-nitrogen material that has a resistivity lower than 450 xcexcxcexa9-cm; heat-treating the trimable resistor element to induce crystallinity; and forming the trimable resistor element that has at least a 10% decrease in resistivity.
The method for fabricating a semiconductor structure that contains an trimable resistor element may further include the step of heat-treating the trimable resistor element in a N2/O2 gas for a time period between about 0.5 hr and about 5 hr, or the step of heat-treating in a N2/O2 gas at a temperature between about 800xc2x0 C. and about 1100xc2x0 C.
The method for fabricating a semiconductor structure that contains a trimable resistor element may further include the step of forming the trimable resistor element in a via opening.
The present invention is still further directed to a method for fabricating a semiconductor structure that contains a diffusion barrier layer which can be carried out by the operating steps of first providing a pre-processed semiconductor substrate; forming an electrical contact on top of the semiconductor substrate; and depositing a layer of refractory metal-silicon-nitrogen on the electrical contact forming the diffusion barrier layer.
The method for fabricating a semiconductor structure that contains a diffusion barrier layer may further include the step of selecting the refractory metal in the refractory metal-silicon-nitrogen from the group consisting of Ta, Nb, V, W and Ti, or the step of forming the diffusion barrier layer with TaSiN containing between about 10 at. % and about 55 at. % Ta, between about 10 at. % and about 45 at. % Si, and between about 30 at. % and about 80 at. % N.